Drafting instrument



' April 15, 1947' G. c. ABRuzzl ET AL 2,`418,860

DRAFT I NG INS TRUMENT Filed March 5, 1945 Patented hf'apr., 15, 1947 STT S DRAFTING IN STRUMENT Gail C. Abruzzi and Marie T. Abruzzi, Chicago, Ill.

3 Claims.

The present invention relates generally to a drafting or engineering instrument of a simple and economical construction and which secures to a maximum degree accuracy in operation.

One of the primary objects of the present invention is to provide a novel and improved construction of drawing instrument which reduces to a minimum the fiexing of the straight edge thereof as is usually occasioned by the straight edge of the parallel link type of draftin'g instrument heretofore used.

A further object of the invention is to pro- Vide a novel, simplified and easily operated construction of a drafting instrument which combines the ruling edges of a protraotor and parallel moving straight edge on a drawing board which simplifies the manipulation of the instrument and accurately maintains the ruling edges against flexing or yielding movement in the use and operation of the same.

These and other objects are accomplished by providing a construction and an arrangement of the various parts in the manner hereinafter described and particularly pointed out in the lappended claims.

Referring to the drawings:

Fig. 1 is a fragmentary top plan view of a parallel moving straight edge in combination with our improved drafting instrument attached thereto; and

Fig. 2 is a cross sectional view taken on the line 2-2 in Fig. 1.

In illustrating the preferred form of our invention we have shown the same in connection with a more or less conventional parallel moving bar or straight edge generally indicated by the reference character IG. This parallel bar or straight edge is preferably, though not necessarily, made of dove-tail cross section main bar II and a lower flat and relatively thinner bar I2 secured together by suitable countersunk screws I3. The upper and lower portions of the bar are provided with the conventional tapered drawing edges |4. The opposite ends of the bar |2 are connected by means of clamping plates I5 to cables IS (only one of which is shown in the drawings). The cables are trained about pulleys (not shown) attached to the drawing board or table in the manner well understood in the art to maintain the straight edge ii] parallel to the upper and lower edges of the drawing board in its movement up and down in the operation of the use of the instrument in a manner well understood in the art. Slidably mounted for longitudinal movement on the straight edge I!! is a Jil base member I'i which has its lower end provided with a transverse dove-tailed recess |8 which is complementary to the dove-tail bar ii of the straight edge II). Located between the lower beveled edge of the dove-tail bar I I and the lower beveled edge of the doVe-tail recess |8 in the base member I'i is a friction plate I9. Extending through the lower edge of the base member I'I and in threaded engagement in suitable apertures therefor are a plurality of horizontally spaced set screws 20 which have their inner ends adapted to seat in recesses 2I in the plate IB for preventing the displacement of the plate 59. These screws 20 also permit the adjustment between the base member Il and the straight edge for taking up the wear when wear oocurs. A11 of these parts may be made of any satisfactory material such as aluminum, wood or plastic or other material which proves satisfactory for the particular purpose or function. The upper portion of the base member I'I is in the form of an annular collar as shown at 22. The annular collar 22 forms in effect a Vertical bore 23 extending therethrough. The collar 22 is pro- Vided with an internal annular recess 24 located at the center thereof. Located in the Vertical bore 23 of the collar 22 is an oscillatable knob or hand grip 25. The hand grip 25 is provided with an annular tapered fiange 26 which is adapted to rest or seat on the upper surface of the annular ring 22 of the base member I'I. The lower portion of the hand grip has a cylindrical portion or hub 21 which protrudes through the Vertical bore 23 of the annular ring 22 and terminates at a point fiush with the bottom of the annular ring 22. Secured to the lower surface of the projecting cylindrical portion 2'I of the knob 25 is a disc or plate 2B which is secured thereto by means of countersunk screws 29. Formed integrally with the plate 23 is a laterally projecting arm 3B to which is secured by means of screws 3I the usual tapered edge ruling bar or ruler 32. Formed integrally with the plate 28 and projecting upwardly adjacent the arm 3B and at right angles with respect thereto is a second arm 33 to which is secured by means of screws 34 a second tapered ruling edge or ruler 35. The ruling edge 35 is therefore located at ninety degrees or right angles with respect to the ruling edge 32. This protractor and ruling edge are frictionally locked in certain positions by spring actuated plungers generally indicated by the reference character 36 located in suitable Vertical bores in the hub portion 21 of the knob 25 so that the lower curved ends of the plungers may seat themselves in suitable curved depressions in the circular plate 28 when the ruling bar 25 reaches the ninety degree position or the position shown in Fig. 1 of the drawings. Mounted in the annular recess 24 and frictionally engaging the Vertical hub portion 2`l of the knob 25 is an arcuate friction bar 3'i. Located in the outer periphery and at the center of the arouate friction bar 31' is the circular recess 38 in which the lower end of an adjustable thumb screw 3B is seated. The thumb screw 39 is mounted in threaded engagement in a threaded aperture 4B formed in one side of the annular ring 22 of the base member il. The protractor in this instance is provided with` the usual graduated scale showing the angular magnitude about the upper surface of the annular member 22 as shown generally at M for permitting the ruling edges 32 and 35 to be adjusted at various angles. i

Summarizing the advantages and functions of operation of our improved drafting instrument, it will Vreadily be seen that by attaching the base member ll directly to the parallel moving straight edge or bar idv and associating the protractor and rulingedges thereof directly with the base member, we have effected a simple, economical and rigid structure and one which reduces to a minimum the fiexing of the parts so that accuracy can be procured in the operation and uselof the instrument. It will also be noted that by providing the plate iii with the adjustable screws EQ for taking up the wear when wear occurs `between these operative parts, we have pro- Vided means ior maintaining the instrument at imaximum efficiency. It will also be noted that b'yattaching a protractor and ruling edge directly: to the parallel moving bar, the overhanging parts such as occasoned by the conventional parallel `link drawing instrument is eliminated so that -no parts thereof interfere with the operationor complete view of the drawing.

While in the above specification we have describ'ed one embodiment which our invention may assume inv practice, it'will, of course, be understood that the same is capable of modification and that vrnodification may bie made without departing from the spirit and scope of the invenv tionas. expressed in the following claims.

What we claim as our inventionand desire to secure by Letters Patent is: v

1. A' drafting instrument comprising a straight edge bar, aV longitudinally extending member. of

dove-tail cross section secured to said bar, a base member having a dove-tail recess complementary to and slidable on said member, a friction plate carried by said base member and engageable with the dove-tail edge of said longitudinal extending member, and means extending through said base member and engageable with said plate for Varying the friction thereon and for retaining said plate'in position.

2. A drafting instrument comprising a drafting straight edge bar, a longitudinally extending member of dove-tail cross section secured to said bar, a base member having a dove-tail recess complementary to and slidable on said member, a friction plate positioned between said member and base, and means for varying the pressure on said plate for retaining said plate in said base.

3. A drafting instrument comprising a drafting straight edge bar, a longitudinally extending member of dove-tail cross section secured to said bar, a base member having a dove-tail recess eompiementary to and slidable on said member, an adj'ustable friction plate between the dovetail edge of said bar in said base member, an annular ring formed integrally with said base member, a hand grip mounted on said ring, a disc secured to the lower side of said hand grip, angularly disposed ruling members secured to said disc, an arcuate friction member carried by said ring and engageable with said hand grip and a thumb screw mounted on said ring and engageable with said friction member for adjusting the frictional tension thereof.

GAIL C. ABRUZZI. MARIE T ABRUZZI.

REFERENCES CITED The following references are of record in the nie of this patent:

UNITED STATES PATENTS Number Name Date 1,1492?? Moffatt Aug. 10,:,1945 1,44l,939 Muller Jan. 9, 1923 1,197268 Cruzen Sept. 5, 1916 13751548 Paulsen Oct. 2,1934 2265,402 Sclocco Dec. 9, 1941 2287,98?v Greenleaf June 30; 1942 2,317,856 Mock Apr. v2'7, 1943 FOREIGN PATENTS' Number Country Date 438,807 GermanV Dec. 26, 1926 

